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Vet’s Advice: Preventing Pinkeye

Face flies are the most important vector in transmission of pinkeye, but ultraviolet light, wind, dust, pollen, tall grass/weeds and grass seed can also irritate eyes.

Infectious bovine keratoconjunctivitis (IBK), or pinkeye, is one of the most common diseases in cow-calf and stocker operations. Pinkeye is caused by a bacteria and/or virus, along with a combination of predisposing factors.

Moraxella bovis is the most common bacteria, but Branhamella ovis and Mycoplasma bovoculi can also be involved. Infectious bovine rhinotracheitis (IBR) virus may also play a role in some outbreaks.

Diagnosing pinkeye is relatively simple. Calves begin with some excess tearing and/or squinting, and the disease can progress to the development of an ulcer in the center of the cornea. Some cases heal on their own, while others need treatment.

As with any disease, prevention is the best strategy. Because pinkeye is a multifactorial disease, a broad-based prevention strategy is needed.

Predisposing factors

Face flies are the most important vector in transmission of pinkeye, but ultraviolet light, wind, dust, pollen, tall grass/weeds and grass seed can also irritate eyes.

Steps to control flies include: fly tags, back rubbers, sprays, dusts, pour-ons and insect-growth regulators. The key to fly control is to have a plan in place that's both timely and effective.

If you use fly tags, do not apply them until there are around 200 horn flies/cow. If tags are put in too early, they can't perform to their optimum level.

Tagging cows is more effective than tagging calves, but the best option is to do both. Check with your herd health veterinarian or Extension beef specialist for timing recommendations in your area. It's ideal to use a spray or pour-on at the same time you fly-tag so you get a quick and significant reduction in fly numbers. Later in the year, timely sprays can also help to reduce the fly population.

Back rubbers and insecticide-impregnated flaps on mineral feeders can be used with good success. Be sure the products are placed in areas where they will get frequent use.

Many nutrition companies market mineral mixes containing insect-growth regulators to control flies. Products include rabon, phenothiazine and methoprene. These products kill 80-90% of the fly larvae that hatch in fresh cow manure.

The key to these products' effectiveness is to start using them a few weeks before the first flies develop. This date will vary by region, so check with a beef specialist from the company that produces the product.

If you have other grazing cattle within about a mile of your operation, those flies could migrate to your herd. If you plan to feed one of these products, try to get neighbors with grazing cattle to do the same.

Fly traps and vaccines
Another fly-control method is a fly trap, a device cattle walk through that mechanically “wipes” flies off the cows. While quite effective for horn flies, its shows limited effectiveness on face flies.

There are a variety of vaccines on the market for pinkeye prevention and control. The concern is there seems to be many isolates of M. bovis that cause disease, and some vaccines contain one or only a few isolates. Check with your herd health veterinarian for recommendations for your herd.

To lessen the chance of mechanical irritation of the eye, pastures should be managed to keep forage in a vegetative state. If pasture gets mature and seed heads develop, the pasture should be clipped.

While IBR can be a cause of pinkeye, using a modified-live virus (MLV) vaccine during an outbreak has been reported to exacerbate the disease. If you're vaccinating nursing calves with an MLV IBR vaccine, do it well ahead of the pinkeye season.

W. Mark Hilton, DVM, is a clinical associate professor of beef production medicine at Purdue University in West Lafayette, IN.